Numerous devices are known which provide a visual indication of the passage of a pre-arranged amount of time. For example, such timing devices or time indicators are useful when attached to perishable items for indicating the length of time the items have been on the wholesaler's or retailer's shelf. Foods, photographic materials and other perishable items can be provided with indicators, which after being activated, evidence a visual change, after the passage of a predetermined period of time. Time-temperature indicators are also known which indicate a visual change as a function of both time and temperature.
Current technologies are typically useful only for short time intervals such as days or weeks. They are not useful for longer time intervals (such as months) because the color change occurs by dye diffusion that begins upon activation. Even though the dye may be very slow in migrating to become visible to the viewer, it is difficult for the observer to identify and determine exactly when the image or color indicates that the predetermined time interval has elapsed. The time interval for the image appearance, from white to colored due to the dye migration (say 10-20% tint) is proportional to the predetermined time for which the time indicator has been designed. Thus, for example, in a three month indicator, the time indicator stays pure white for about a month, after which, the indicator starts to change color. After about three months, the observer sees a definite color change of, say 10-20% tint. During the time interval between one and three months, the time indicator is in a “grey area”, i.e., “The Grey Time”, between expired and unexpired subject to interpretation by the viewer. This lack of a sharp transition time is the problem with known simple dye diffusion systems and indicators.
More specifically, many of the known time indicators, which are generally short-term time indicators, are based on the gradual migration of ink from one substrate through another substrate, i.e. in a path perpendicular to the surface of the substrate. After the ink migrates through the substrate(s) it is viewed on a display surface to thereby indicate that the predetermined time period has elapsed.
Examples of such time indicating systems include the following U.S. patents:
U.S. Pat. No. 4,212,153 to Kydonieus et al. describes a laminated time indicator. In general, the Kydonieus patent discloses a time color indicator having a reservoir layer adhesively attached to an indicator layer. In accordance with the Kydonieus patent, a migrating agent in the reservoir layer migrates through the adhesive layer and the indicator layer to the top or front surface of the indicator layer. The Kydonieus patent also teaches that the reservoir layer is preferably mounted on a barrier layer with an adhesive and release sheet on top of the reservoir layer. The indicator is activated by removing the release sheet and applying an indicator layer to the adhesive layer. Alternatively, the adhesive and release sheet may be associated with the indicator layer. Kydonieus further teaches that the indicator layer is a solid sheet or film of non-porous polymer which allows migration of the chosen agent, and that appropriate indicator layer materials include plasticized PVC, semi-plasticized PVC, rigid PVC, acrylics, polyurethanes and Hytrel® (Dupont Company). The Kydoniesus indicator layer is 2 to 14 mils thick, and may contain plasticizers and stabilizers. The reservoir layer is preferably made from a plastisol, although vinyl chloride/vinyl acetate copolymer, a urethane polymer, a polyolefin, Hytrel® and polyvinyl chloride may be used in forming the reservoir layer. Kydonieus teaches that the reservoir layer should be 1 to 20 mils thick, and is preferably 1 to 5 mils thick. Kydonieus also contemplates that the reservoir layer may be layered down as an ink onto the barrier layer. Specifically, Kydonieus contemplates printing the reservoir composition on mylar or aluminum foil. The Kydonieus patent suggests that appropriate adhesives include thermosetting or thermoplastic pressure-sensitive acrylics or rubbers. The adhesive layer can be preformed and applied as a sheet, applied with another layer such as a release sheet or by coating.
U.S. Pat. No. 5,364,132 to Haas et al. describes a method of assembly and activation of a reusable self-expiring Security Identification Badge. The Badge includes a base substrate having a void indicia area, an ink substrate having an expired indicia area of a soluble ink and an adhesive surface, and an overlay substrate having an ink dissolver and a display surface. When the Security I.D. Badge is issued, the inked substrate is attached to the base substrate, the inked substrate covering the void indicia area. The overlay substrate is then placed over and attached to the inked substrate, the ink dissolver in contact with the soluble ink of the ink substrate. The ink dissolver of the overlay substrate contacts and coacts with the soluble ink of the inked substrate to dissolve the ink and allow the ink to migrate through to the overlay substrate to the display surface, where it can be visually perceived, in a preselected time interval.
U.S. Pat. No. 5,446,705 to Haas et al describes a time indicator that changes color or produces an image or information after a specific time interval. The time indicator includes a base substrate with colored dye deposited on a first surface; and a substrate having an adhesive on a first surface thereof, the adhesive positioned at discrete locations on the first surface of the substrate. The substrate and the base substrate are put into adhesive contact. The adhesive contacts and coacts the colored dye to dissolve the dye and permit the dye to migrate through the adhesive to cause a color change visible through the substrate. The discrete adhesive inhibits lateral migration of the dye to preserve the image or information of the dye in a clear and/or understandable condition.
U.S. Pat. No. 5,602,804 to Haas describes a time indicator device with a display layer with at least one defined display region therein. A migration layer is provided which overlies and is attached to the display layer. The migration layer has at least one migration region therein and in use each migration region is in contact with at least one display region. An activation layer is provided which has at least one defined activation region therein. The activation region includes a migrating agent capable of migrating laterally through the migration region. When the activation layer overlies the migration layer, each activation region overlies at least one migration region. The migration region connects each activation region with at least one display region which is laterally distal from the activation region. In use and in order to activate the device the activation layer and migration layer are adhesively attached to each other. When the activation layer is contacted with and overlies the migration layer, each activation region contacts at least one migration region. Upon contact the migrating agent is activated to migrate laterally from the activation region through the migrating region to at least one display region in a predetermined amount of time to cause an indication in the display region that the predetermined amount of time has elapsed. Preferably, the device has a plurality of defined display regions, defined activation regions and/or migration regions to provide a means for adjusting the predetermined time, adjusting for environmental conditions and to provide a plurality of elapsed times.
U.S. Pat. Nos. 5,715,215 and 5,873,606 to Haas et al describe an identification badge that comprises a base coated with an adhesive protected by release paper. This badge is assembled by removing the release paper, placing an identification card into contact with the adhesive, and then attaching a fastener through a slot in the base of the badge. Various fasteners may be used to attach this badge to wearer's apparel. The identification card can also be mounted so that the identification indicia is placed against a transparent, adhesive and viewed through a transparent base. A timing indicator can be incorporated into the badge so as to show the expiration of the badge after a selected period of time.
U.S. Pat. No. 5,719,828 to Hass et al. describes a patterned indicator which contains latent information. The patterned indicator includes a first substrate having first and second surfaces, the first surface having a uniform pattern printed of an ink thereon. A second transparent substrate having first and second surfaces is also provided. An adhesive activator is provided on the first surface of the second substrate. The indicator is activated by placement of the first surfaces of the first and second substrates into adhesive contact such that the ink and adhesive activator coact to cause the ink pattern to gradually bleed and blend together to cause a change visually perceptible through the transparent substrate in a selected time interval. A preferred embodiment of the invention is a parking permit, while other preferred embodiments include transit tickets, admission tickets, time passage indicators for other applications. Also within the scope of this invention are patterned indicators printed with inks having multiple sensitivities for indicating tampering with goods in packages sealed with such indicators.
U.S. Pat. No. 5,785,354 to Hass describes an identification band is provided which includes an elongated band having an outer surface, an inner surface and first and second ends. A first chemical composition, e.g., a soluble ink, is distributed on the outer surface of the band proximate the first end. A display region is disposed in the band proximate the second end. A second chemical composition, e.g., an adhesive ink activator is distributed on the inner surface of the band overlying the display region proximate the second end. When the band is wrapped around an object, e.g., a user's wrist, with the outer surface exposed, the outer surface of the first end and the inner surface of the second end overlay and are in contact, preferably in adhesive contact, with each other. The first and second chemical compositions coact with each other to cause a visually perceptible change in the display region after a predetermined time interval.
U.S. Pat. No. 5,822,280 to Haas describes a time indicator that includes a front layer and a back layer, each having an inner and outer surface. The front layer has a display region on its outer surface. An adhesive means is provided on the inner surface of the front or back layer for adhesively attaching the front layer and back layer to each other. An opaque viewing layer is included on the front or back layer and an activation agent is provided on the other layer. One surface of the opaque viewing layer is viewable from the display region when the front and back layers are adhesively attached to each other. A dye that is substantially non-migrating through the opaque viewing layer, overlies the other surface of the opaque viewing layer. When the inner surfaces of the front and back layers are contacted with each other, the adhesive means adhesively attaches the front and back layers to each other and activates the activation agent. The activation agent migrates to the opaque viewing layer in a predetermined period of time to be absorbed therein. Such absorption activates the dye to enable it to migrate through the opaque viewing layer toward the other side causing an indication in the display region that the predetermined amount of time has expired. Optionally, the activation agent contacts the dye to, for example, solubilize the dye to enable it to migrate through the opaque viewing layer. Preferably, the activating agent is a plasticizer that is absorbed into the polymeric opaque viewing layer. At a critical concentration of the plasticizer in the viewing layer, the dye is rapidly absorbed into the viewing layer, passing through the viewing layer to the other surface thereof where it becomes visible through the clear display region on, for example, the white background of the viewing layer.
U.S. Pat. No. 5,930,206 to Haas describes a time indicator comprising a front part and a rear part, the rear part comprising an ink pattern layer overlaying a rear support member. The front part comprises a transparent front support layer, and an opaque adhesive layer having a front ink display surface, the adhesive layer capable of dissolving the ink pattern on the rear part, whereby contacting the front part with the rear part by applying the opaque adhesive layer onto the ink pattern layer activates the dissolution and migration of ink in a selected time interval from the ink pattern layer, through the opaque adhesive layer to the front ink display surface for viewing through the transparent front support layer.
U.S. Pat. No. 5,957,458 to Haas et al describes a game card having a hidden game image thereon that is developed over a predetermined period of time. The game card includes a front part and a rear part. The rear part has a migrating ink pattern layer overlaying a rear support member to form a game image. An non-migrating printed pattern layer overlays the rear support member to form a confusion pattern to hide the image. The front part includes a front support layer having an adhesive layer on one side and a front ink display surface on the other side. The adhesive layer is capable of causing the migrating ink pattern to migrate upon contact therewith. Thus when the front part is contacted with the rear part by applying the adhesive layer onto the ink pattern layer, the adhesive layer activates the migration of ink in a selected time interval from the ink pattern layer, through the adhesive layer to the front ink display surface for viewing the game image. Typically, the game image is capable of informing the user whether the game card is a winning card or a losing card.
U.S. Pat. No. 5,974,003 to Pedicano et al. describes a time color indicator that includes a base layer segment having a transparent impermeable layer, a substantially non-curing opaque coating, and a release sheet. A portion of the uncoated surface of the transparent layer bears a printed area including a camouflage pattern printed with non-migrating ink and a message segment printed with migrating ink. An indicator layer segment includes a transparent impermeable layer, a substantially non-curing opaque coating, and a release sheet partially folded back to form a finger gripping tab and expose an indicator layer coating portion which contacts and adheres to the base layer adjacent the printed area. The time color indicator is activated by pulling the finger tab to remove the release sheet, causing the indicator layer coating to cover and contact the printed area, with the message segment migrating through the indicator layer coating.
One of the problems associated with all of the foregoing devices is that they are difficult to adjust for a selected period of time. Adjustment often involves experimentation with many types of inks, solvents, wicks, etc. to prepare a device, which can operate under the conditions expected. Additionally, very few of these devices can indicate the relative length of time that has elapsed since the device was activated, i.e., it is difficult to determine what fraction of the predetermined period of time has elapsed. Further, none of these devices are suitable for measuring a relative long time period. Most of the prior art devices gradually change color over a relatively short period of time and involve, at best, a guess on how much time has elapsed. When this is combined with the possible variations in temperature, humidity, etc. that may exist in the environment of the time indicator, the viewer has very little confidence that he is close to the expiration time of the device.
It is an object of this invention to provide a time indicator device, which can provide the user with a clear indication of the passage of relatively long time intervals.